Though researchers described the results of the study, which involved the injection of human stem cells into pig embryos, as "highly inefficient," it brings the scientific field one step closer to discovering if it's feasible to grow custom human organs inside an animal for patients in dire need of transplants.

Producing chimeras (organisms that contain cells from two species) remains controversial, but Ju Wu, the lead author of the study, said a change in perspective would pave the way for the hybrid embryos to be perceived as a sort of miraculous force--one that's meant to alleviate the world's growing organ shortage.

“In ancient civilizations, chimeras were associated with God,” he said to National Geographic, and our ancestors thought “the chimeric form can guard humans.”

In a separate interview, Wu said it wasn't their intention to create a monster, but one that could help resolve a global health problem.

The statistics are troubling. Every ten minutes, according to the Organ Procurement & Transplantation Network, a person is added to the national transplant waiting list. On average, 22 people with fatal conditions on the waiting list die each day.

Acknowledging the controversy, scientists elected to restrict development of the interspecies embryo to one month so that they could achieve a better understanding of how cells mix, differentiate and integrate, one professor involved in the study told the BBC.

Until August 2015, the National Institutes of Health had a moratorium on funding for chimera experiments. One stem cell researcher, Sean Wu, described the lifting as "a step in the right direction," but also said that some uncertainty remains.

"We still don’t know what the outcome will be case by case,” he added.